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Carburator Drag
Brakes Demand on NASCAR Super Speedways
It might seem counter-intuitive but there are so many details that these NASCAR teams take into account when it comes to choose the proper brake package to run at Daytona and Talladega. The brake demand is of course less as opposed as Intermediates and Short Tracks in terms of pressure and temperature but there are other variables and parameters that come into play and every team must be aware of.
The main target for a speedway car is the aerodynamics, they even clear coat the decals, every little thing counts.
As far as the brakes are concerned, the brake package that includes the caliper/rotor combination must be as light as possible but still strong enough to come down pitroad and slow those 3600lbs cars from 195 to speed in pit road safely and in the shortest amount of time. Over the past years the brake makers have made huge efforts to come up with a proper engineered brake package and the state-of-the-art has come a long way. As mentioned, the weight is crucial for every component that is on a race car, especially for the COT where the teams have been left in a little box to work within, the weight of the brakes and unsprung weight can give them an edge to be more competitive than the next car. Some pads prototypes had been developped, with full thickness but party made out of carbon and few mm of real friction material to reduce the pad weight.
Second important requirement is to reduce the drag of the brake pads "rubbing" on the rotor faces. Of course turning left only, the pads facing inward the race track inevitably rub the inner rotor faces due to lateral G, we see this especially at Daytona rather than Talladega that has got higher bankings. To overcome this dragging issue the calipers and pads are usually equipped with a sort of pad retraction device such as springs to keep the pad off the rotors.
Plus, still related to reducing the brake drag, is the instantenous release, that is the capability of the seals to pull the pistons back everytime the driver gets on the brakes and releases them. It's just a split second but it makes the difference between win the race and finish mid-pack at Talladega. The release can be measured at the dyno or by performing speed coast down test sessions at the proving grounds - it is of course crucial for this type of test to quantify the influence of external factor such us wind, temperature, tires, track conditions, ecc... To improve the release the calipers come with special seals called High Roll Back. The other thing they can do is to run brake pad materials which are softer than std for better release.
In actuality, the driver gets on the brakes on speedways in the following instances:
1. Heavy, to come down pitroad for a greenflag pitstop. It's important the pedal is there. Most times the spotter comes on the radio to remind the driver to pump the brakes.
2. Heavy, to avoid the wrecks "the Big One". At the time I am writing this article, todays race at Talladega had to 2 big ones one involved R Newman, the other one M Martin and Talladega is statistically known to have at least one
3. At Daytona, the car handling comes into play. The tires get old or the car gets tightened up so the driver might just tap the brakes to help the handling.
4. The leader might tap on the brakes a little bit to cause the chasers to step on the brakes. Absolutely never lift off the throttle on speedways, not to kill that momentum, with NASCAR mandating the carburator restrictor plates, it takes too long to the engines to gain RPMs back.
5. Drafting and avoing to get bumper to bumper. With the new rule NASCAR established, they want to see day light between bumpers over the corners, so again the might just get on the brakes a little bit but never lift the throttle.
Getting back to point #1, it takes a lot of clamping force to slow down these cars so the caliper piston size is bigger than std. This is because of 3 reasons mainly: a. The brakes are cold so the pads are not within their operating temperature, as a result the grip is mechanical only not thermo-chemical. b. The pad materials for speedways are usually less grippy than those ones for Short Tracks and Road Courses. c. The rotors are usually of smaller diameter - and as a result the brake effective radius is smaller - to save weight and reduce the inertia due to rotating mass.
The Master Cylinder size is also bigger than a std size. This is because of 3 reasons: a. To run with a bigger caliper but at the same time keeping same BIAS, pedal ratio, etcc.. b. To compensate the volume of fluid due to the rotor runout and vibrations pushing the pads back, this happens running at big tracks for many laps without never hitting the brakes then suddently on the brakes, the pedal feels now longer. c. To get more modulation coming down in the pits and reduce the possibility of locking up the front wheels and get past the pitstall - the speedway brake package is typified by a brake BIAS towards the fronts as opposed as Short Tracks.
Brakes problems can happen on speedways most times due to rotor thermal shock coming down pitroad with cold brakes.
The hardest part is to get the brake package to work in harmony with the whole car.
About the Author
Riccardo DiSilvestro, Mechanical Engineer out of University of Rome "La Sapienza" with 10yrs experience in Motorsports is Engineering Manager in Charlotte, NC
Do ATV's always run poorly compared to cars and trucks?
I am completely fed up with our Kawasaki Prairie 650 ATV. the sucker has always been balky in cold weather, and we have to get it fixed twice a year.
our 20 year old cars and trucks have always been more reliable than this piece of junk.
Are ATV's always this way, or are Kawasakis just crap?
If we get a new one (different BRAND) with fuel injection, will it run better?
It is 28 degrees F outside, and the thing is balkier than an old carburator car when it was 30 below zero. It was ALWAYS crappy like this, even brand new. Then there are stupid belts that need changing after not much use, etc.
tx for answers!
we use it for snowplowing a 1./4 mile driveway and dragging deer.
If you have an opinion on a replacement brand, please tell me. reliability is my top priority.
A usual problem with ATVs in snowy climates is snow getting into the air filter/intake and stops the engine from breathing. I have an old model automatic 750cc honda that iv used for about 3 years (second hand 2 years before me) it run's great, and yes i would say kawasaki are bad ATV developers just because its so hard to get new replacement parts! and we use our quad for the same thing you do as well as carrying large loads up mountainous regions. don't know if i can help you anymore.
F-6 CAT,IQ POLARIS 600,MXZ 600SDI AND MXZ 600 CARB DRAG RACE